kernel/linux.git/tools/tracing/rtla/src/timerlat.c, branch v7.2-rc1

rtla/timerlat: Add -A/--aligned CLI option

2026-05-28T11:02:48+00:00

Add a new option, -A/--aligned, that enables timerlat thread alignment implemented on the kernel-side in commit 4245bf4dc58f ("tracing/osnoise: Add option to align tlat threads"). The option takes an argument, representing alignment between timerlat threads in microseconds. The feature is modeled after the option of the same name in the cyclictest tool. Link: https://lore.kernel.org/r/20260527144928.2944472-1-tglozar@redhat.com Signed-off-by: Tomas Glozar

rtla: Parse cmdline using libsubcmd

2026-05-28T11:02:48+00:00

Instead of using getopt_long() directly to parse the command line arguments given to an RTLA tool, use libsubcmd's parse_options(). Utilizing libsubcmd for parsing command line arguments has several benefits: - A help message is automatically generated by libsubcmd from the specification, removing the need of writing it by hand. - Options are sorted into groups based on which part of tracing (CPU, thread, auto-analysis, tuning, histogram) they relate to. - Common parsing patterns for numerical and boolean values now share code, with the target variable being stored in the option array. To avoid duplication of the option parsing logic, RTLA-specific macros defining struct option values are created: - RTLA_OPT_* for options common to all tools - OSNOISE_OPT_* and TIMERLAT_OPT_* for options specific to osnoise/timerlat tools - HIST_OPT_* macros for options specific to histogram-based tools. Individual *_parse_args() functions then construct an array out of these macros that is then passed to libsubcmd's parse_options(). All code specific to command line options parsing is moved out of the individual tool files into a new file, cli.c, which also contains the contents of the rtla.c file. A private header, cli_p.h, is added alongside the public header cli.h, so that unit tests are able to test statically declared option callbacks. Minor changes: - The return value of tool-level help option changes to 129, as this is the value set by libsubcmd; this is reflected in affected test cases. The implementation of help for command-level and tracer-level help is set to 129 as well for consistency, and the change is reflected in exit value documentation. - Related to the above, {rtla,osnoise,timerlat}_usage() are marked __noreturn and exit() is removed from after they are called for cleaner code. - The error messages for invalid argument for options --dma-latency and -E/--entries were corrected, fixing off-by-one in the limits. Note that unsetting options (using --no- syntax) is currently not implemented for options that use custom callbacks. For --irq and --thread, it will never be implemented, as they conflict with already existing --no-irq and --no-thread with a different meaning. Assisted-by: Composer:composer-1.5 Link: https://lore.kernel.org/r/20260528103254.2990068-5-tglozar@redhat.com Signed-off-by: Tomas Glozar

rtla: Stop the record trace on interrupt

2026-05-18T09:00:52+00:00

Before, when rtla got a signal, it stopped the main trace but not the record trace. With "--on-end trace", this can lead to save_trace_to_file() failing to keep up, especially on a debug kernel. Plus, it adds post-stoppage noise to the trace file. Signed-off-by: Crystal Wood Fixes: c73cab9dbed0 ("rtla/timerlat_hist: Stop timerlat tracer on signal") Fixes: a4dfce7559d7 ("rtla/timerlat_top: Stop timerlat tracer on signal") Fixes: 3aadb65db5d6 ("rtla/timerlat: Add action on end feature") Link: https://lore.kernel.org/r/20260512173731.2151841-1-crwood@redhat.com Signed-off-by: Tomas Glozar

rtla/timerlat: Simplify RTLA_NO_BPF environment variable check

2026-03-11T14:29:50+00:00

The code that checks the RTLA_NO_BPF environment variable calls getenv() twice and uses strncmp() with a length of 2 to compare against the single-character string "1". This is inefficient and the comparison length is unnecessarily long. Store the result of getenv() in a local variable to avoid the redundant call, and replace strncmp() with strncmp_static() for the exact match comparison. This follows the same pattern established in recent commits that improved string comparison consistency throughout the rtla codebase. Signed-off-by: Wander Lairson Costa Link: https://lore.kernel.org/r/20260309195040.1019085-15-wander@redhat.com Signed-off-by: Tomas Glozar

rtla: Use str_has_prefix() for option prefix check

2026-03-11T14:29:50+00:00

The argument parsing code in timerlat_main() and osnoise_main() uses strncmp() with a length of 1 to check if the first argument starts with a dash, indicating an option flag was passed. Replace this pattern with str_has_prefix() for consistency with the rest of the codebase. While character comparison would be slightly more efficient, using str_has_prefix() provides better readability and maintains a uniform coding style throughout the rtla tool. Signed-off-by: Wander Lairson Costa Link: https://lore.kernel.org/r/20260309195040.1019085-14-wander@redhat.com Signed-off-by: Tomas Glozar

tools/rtla: Remove unneeded nr_cpus from for_each_monitored_cpu

2026-03-09T07:49:17+00:00

nr_cpus does not change at runtime, so passing it through the macro argument is unnecessary. Remove the argument and use the global nr_cpus instead. Signed-off-by: Costa Shulyupin Link: https://lore.kernel.org/r/20260306194953.2511960-5-costa.shul@redhat.com Signed-off-by: Tomas Glozar

tools/rtla: Consolidate nr_cpus usage across all tools

2026-03-09T07:49:16+00:00

sysconf(_SC_NPROCESSORS_CONF) (via get_nprocs_conf) reflects cpu_possible_mask, which is fixed at boot time, so querying it repeatedly is unnecessary. Replace multiple calls to sysconf(_SC_NPROCESSORS_CONF) with a single global nr_cpus variable initialized once at startup. `#pragma once` in timerlat_u.h is needed for pre-C23 compilers to avoid redefinition errors. Signed-off-by: Costa Shulyupin Link: https://lore.kernel.org/r/20260306194953.2511960-2-costa.shul@redhat.com Signed-off-by: Tomas Glozar

rtla/timerlat: Add --stack-format option

2026-03-04T14:51:56+00:00

In the current implementation, the auto-analysis code for printing the stack captured in the tracefs buffer of the aa instance stops at the first encountered address that cannot be resolved into a function symbol. This is not always the desired behavior on all platforms; sometimes, there might be resolvable entries after unresolvable ones, and sometimes, the user might want to inspect the raw pointers for the unresolvable entries. Add a new option, --stack-format, with three values: - truncate: stop at first unresolvable entry. This is the current behavior, and is kept as the default. - skip: skip unresolvable entries, but do not stop on them. - full: print all entries, including unresolvable ones. To make this work, the "size" field of the stack entry is now also read and used as the maximum number of entries to print, capped at 64, since that is the fixed length of the "caller" field. Link: https://lore.kernel.org/r/20260119115222.744150-1-tglozar@redhat.com Signed-off-by: Tomas Glozar

rtla: Remove unused headers

2026-01-07T14:57:55+00:00

Remove unused includes for and to clean up the code and reduce unnecessary dependencies. Signed-off-by: Wander Lairson Costa Link: https://lore.kernel.org/r/20260106133655.249887-12-wander@redhat.com Signed-off-by: Tomas Glozar

rtla/timerlat: Add --bpf-action option

2026-01-07T14:57:16+00:00

Add option --bpf-action that allows the user to attach an external BPF program that will be executed via BPF tail call on latency threshold overflow. Executing additional BPF code on latency threshold overflow allows doing low-latency and in-kernel troubleshooting of the cause of the overflow. The option takes an argument, which is a path to a BPF ELF file expected to contain a function named "action_handler" in a section named "tp/timerlat_action" (the section is necessary for libbpf to assign the correct BPF program type to it). Link: https://lore.kernel.org/r/20251126144205.331954-3-tglozar@redhat.com Signed-off-by: Tomas Glozar